Method and device for determining the probable path to be covered by a vehicle

ABSTRACT

A method and a device for determining a future travel-course progression or travel-course range of a vehicle whose traveling speed is controllable as a function of a distance to preceding-traveling vehicles, the future course range being determined at least on the basis of a course progression of one preceding-traveling vehicle. Moreover, a lateral offset is determined for all detected preceding-traveling vehicles. The determined future course range is limited on the basis of detected stationary objects.

The present invention relates to a method and a device for determining afuture travel-course range of a motor vehicle. For example, it can beused within the framework of an adaptive cruise control or proximitycontrol of a vehicle, an adaptive headlight-leveling adjustment, or evensimply for detecting critical situations. It is assumed that the vehicleis equipped with at least one sensor which is able to detect vehiclestraveling in front and stationary objects in the forefield of thevehicle, and at least determine their position. Such sensors can beconstructed, for example, as radar-, laser-, or even as video sensors.The present invention is preferably used in conjunction with an adaptivecruise control or proximity control of a vehicle, since such a sensor isalready provided for this application.

BACKGROUND INFORMATION

Numerous publications deal with an automatic control of the speed of amotor vehicle, taking into consideration the distance to vehicles infront. Such systems are frequently designated as adaptive cruise control(ACC), or in German as adaptive or dynamic traveling-speed controllers.In view of today's traffic conditions, a basic problem in such systemsis an automatic decision as to which of several preceding-travelingvehicles is relevant or the most relevant for the cruise or proximitycontrol. This decision is particularly difficult when the road uponwhich the controlled vehicle is moving is multi-lane and curvy. In thiscase, a proximity sensor which, inter alia, is used for detectingvehicles in front, generally also detects vehicles that are located onadjacent traffic lanes and therefore have only secondary relevance for aproximity control.

Accordingly, there is a need in an ACC system to determine a futuretravel-course progression or a future travel-course range of thecontrolled vehicle in order to ascertain in each case the most relevantvehicle in front or, conversely, the most dangerous obstacle at aninstantaneous point of time based on the knowledge of this range. Bothvariables—the course progression and the course range—are basicallyoriented to the run of the road, but in the optimum case, also take intoaccount lane-change or turning operations of the controlled vehiclepossibly taking place. In this context, the term “future course range”differs in the following from the term “future course progression” tothe effect that it includes the entire spatial range in which thecontrolled vehicle will probably move. This means that it also takesinto account the breadth necessary for the motor vehicle in each case.

Presently known solutions to the problem formulation indicated above aredescribed, for example, in the publication “Adaptive CruiseControl—System Aspects and Development Trends” by Winner, Witte et al.,published as SAE Technical Paper Series No. 961010 at the SAE of Feb.26-29, 1996. According to that, the easiest way of predicting a futurecourse of a controlled vehicle is to assume a linear movement. However,it is obvious that this type of predicting will not function in the caseof curves or lane changes. A more complex case, which, however,furnishes adequate results for wide ranges, is the assumption of acourse having a constant curve. This is determined, for example, from adifference of wheel speeds, from a steering angle or steering-wheelangle, from transverse accelerations and/or from yaw rates.Corresponding methods are known from the field of operating-dynamicscontrol. The disadvantage of this method is that, in each case, thefuture course or course range is estimated only on the basis of thecurrent course. Thus, errors arise here as well in response to eachchange of the course, such as when driving into or out of curves. Afurther possibility for predicting a course progression, which islikewise mentioned in the publication indicated, is the use ofnavigation systems. However, the limits of this method depend upon howup-to-date and accurate the available maps are, as well as the abilityof the system to determine the current position of the vehicle. Theprediction is faulty particularly in construction-site areas or in thecase of new roads. Another possibility indicated in the aforesaidpublication is a prediction of the road progression or of the lane basedon radar data. Stationary objects such as reflectors or crash barriers,which are detected by a signal processor, are used to reconstruct theroad boundaries. However, according to the publication, little is knownat this point about the quality and reliability of this method.

U.S. Pat. No. 4,786,164 describes a system and a method for detecting adistance between two vehicles moving in the same traffic lane. Thetraffic lane in which each of the two vehicles is moving is determinedon the basis of a comparison of angles at which reflectors, which aredistributed at both sides of the road, are detected. However, the methoddescribed in that case is applicable only if suitable reflectors areactually available on both sides of a road, and thus is dependent uponinfrastructure conditions.

German Patent No.196 14061 describes a system for controlling thedistance to a vehicle in front on the basis of an adjustable probabilitydistribution. This described system has a curve-determination device, inwhich the curve of a road is determined on the basis of a steering angleand a vehicular speed. To improve reliability, according to a firstmodification, the steering angle is ascertained on the basis of themovement of a specified stationary object. To that end, the locations ofa stationary object relative to a moving system vehicle are monitored atuniform time intervals. The locations are then defined as circular arcsin order to calculate the curve of the road upon which the systemvehicle is traveling. According to a second modification, a sharp curveof the road can likewise be detected with reference to a stationaryobject. According to a fourth modification, the calculated curve can beincreased or reduced when a turn indicator indicates the right or theleft direction. According to a tenth modification, with the aid of anavigation system such as a GPS system, it is possible to determinewhether or not a curve exists in a forward direction of the systemvehicle. However, none of the methods put forward in this patenteliminates the disadvantages already indicated in detail.

SUMMARY OF THE INVENTION

An object of the present invention is to specify a method and a devicebased thereon which make it possible to reliably determine a futuretravel-course range of a first vehicle, and particularly when drivinginto and out of curves, as well.

This objective is achieved according to the present invention in thatthe future course range of the first vehicle is determined at least withreference to a course progression of a vehicle in front. To that end,according to a preferred embodiment of the present invention, a relativeposition of at least one preceding-traveling vehicle with respect to thefirst vehicle is determined, and subsequently a lateral offset q betweenthe vehicle in front and the first vehicle is determined based on thisrelative position. The future course range of the controlled vehicle isthen determined as a function of the lateral offset q and of the courseprogression of the vehicle in front. Concretely stated, the movement ofone or more preceding-traveling vehicles is observed to ascertain thefuture course progression or course range of the controlled vehicle.Lateral offset q is advantageously re-determined at fixed or selectablepoints of time, and is assumed to be constant between these points oftime. It is particularly advantageous if the future course range of thecontrolled vehicle is determined on the basis of course progressions ofa plurality of preceding-traveling vehicles, a lane change of a singlepreceding-traveling vehicle being isolated by comparison or correlationor average of the course progressions of all preceding-travelingvehicles, according to a particularly preferred refinement of thepresent invention, in addition to the first future course rangedetermined according to the present invention, at least one furtherfuture course range is ascertained on the basis of a steering angle, asteering-wheel angle, a yaw rate, a difference of wheel speeds, or atransverse acceleration of the controlled vehicle, or with reference tostationary objects, or on the basis of oncoming vehicles which aredetected by the proximity sensor of the first vehicle. A verified futurecourse range is then ascertained on the basis of the first and the atleast one further determined future course range. Concretely stated,this means that a future course range of the controlled vehicle isdetermined on the basis of different methods which are independent ofone another. By combining these individually determined, future courseranges, it is possible to correct errors occurring individually in themethods, so that the verified future course range includes an optimalprediction of the actual course range. According to a furtheradvantageous refinement of the present invention, the future or theverified future course range is limited on the basis of positions ofdetected stationary objects, or based on positions of detected oncomingvehicles. In this manner, further independent data flow into thedetermination of the future course range.

One particular advantage of the method of the present invention is thatthe future course range is ascertained on the basis of measuring data ofsituations which actually lie in the forefield of the controlledvehicle. Instead of an estimation by extrapolating an instantaneoussituation, an evaluation is made of the situation actually existing inthe forefield of the vehicle. In particular, this permits earlydetection of a beginning or end of a curve. In this manner, the errorrate is markedly reduced compared to previously known methods. A furtheradvantage is that the method is independent of special infrastructureconditions such as reflectors provided extra at the edge of the road.However, if appropriate reflectors are present, they can be suitablytaken into account as well. In addition, the method can be implementedin a vehicle which is equipped with an adaptive cruise control withoutspecial expenditure, in particular without an additional image pick-upand image evaluation device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a basic representation of a device according to the presentinvention.

FIG. 2 shows a first diagrammatic sketch to clarify the method of thepresent invention.

FIG. 3 shows a second diagrammatic sketch to clarify the method of thepresent invention.

FIG. 4 shows a flow chart according to a first exemplary embodiment ofthe present invention.

FIG. 5 shows a flow chart according to a second exemplary embodiment ofthe present invention.

FIG. 6 shows a flow chart for the detailed clarification of the methodof the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a device for carrying out the method of the presentinvention. A proximity sensor 10, such as a radar or laser sensor, isconnected to an evaluation and control unit 11. Evaluation and controlunit 11 receives numerous further signals, of which an input 13 for avehicle's own speed, an input 14 for a steering angle and an input 15for a yaw rate are shown here by way of example. Evaluation and controlunit 11 is also connected to one or more actuators 12. The entire deviceis installed in a first vehicle. According to known methods, proximitysensor 10 is used to detect preceding-traveling vehicles, oncomingvehicles, as well as stationary objects upon and on both sides of theroadway. Corresponding measuring data are prepared and supplied toevaluation and control unit 11. According to the following describedmethod, this unit determines at least one future travel-course range ofthe first vehicle. Evaluation and control unit 11, by way of actuator(s)12, controls or regulates the speed of the vehicle within the frameworkof an adaptive cruise control. Alternatively or in addition, by way ofactuators 12, the unit controls, for example, the light level or thelight cone of the vehicle headlights, or generates a warning signalindicating a critical situation.

FIG. 2 shows a two-lane road 20, upon which two vehicles 21, 22 aremoving in the same direction. Numeral 21 indicates the vehicle havingthe device of the present invention. Starting from the front of vehicle21, an angle range 24 is sketched which symbolizes the detecting rangeof proximity sensor 10. A dot-dash line 26 shows the future courseprogression of vehicle 21. A line segment 23 indicates a lateral offsetq between vehicles 21 and 22. Numeral 25 indicates a stationary objectsuch as a tree at the edge of the road.

FIG. 3 likewise shows a two-lane road 30, upon which three vehicles 31,32 and 33 are shown at two different instants t₀ and t₁. The positionsof the vehicles at instant t₀ are shown with a dotted line and aredesignated by 31 a, 32 a and 33 a. The positions of the vehicles atinstant t₁ are designated by 31 b, 32 b and 33 b. Two line segments 34and 35 designate a lateral offset q₁ and q₂, respectively, betweenvehicles 31 and 32 and between vehicles 31 and 33.

FIG. 4 shows a flow chart of a first exemplary embodiment of the presentinvention. According to step 41, preceding-traveling vehicles F_(vi) aredetected with the aid of proximity sensor 10. In so doing, according toFIG. 2 and FIG. 3, vehicle 22 as well as vehicles 32 and 33 aredetected. In step 42, a position P_(vi) of each individualpreceding-traveling vehicle is determined. Depending upon theimplementation, this step can be carried out either by an evaluationcircuit within proximity sensor 10 or by evaluation and control unit 11.The determined positions P_(vi) of preceding-traveling vehicles F_(vi)include a distance d_(i) and an angle α_(i). According to step 43, alateral offset q₁, indicated in FIGS. 2 and 3 by line segments 23, 34and 35, is ascertained. Purely mathematically, lateral offset q₁ isexpressed as

q₁=d_(i)*sin α_(i).

However, since the curve of roads 20 and 30, respectively, and anadditional lateral offset of vehicles F_(vi) resulting from this are notallowed for in this equation, it is more advantageous to ascertain therespective lateral offset q₁ based on position P of vehicle 31 atinstant t₁ and position P_(vi) of preceding-traveling vehicles 32, 33 atinstant t₀. In other words, in this context, lateral offset q₁ is firstdetermined in each case when first vehicle 31 is located at or next tothe position which the respective preceding-traveling vehicle held oneor more measuring instants previously.

According to step 44, future course range KB of controlled vehicle 21,31 is now determined on the basis of an assumed width b of the firstvehicle, with reference to course progressions KV_(i) ofpreceding-traveling vehicles F_(vi), with reference to their respectivelateral offset q₁ and, optionally, with reference to previouslydetermined course progressions. This is based on the assumption that thefirst vehicle will continue to move like the vehicle(s) in front. If anintended or beginning lane change by the vehicle is detected, forexample as a function of a blinker signal, the determined probablecourse range is advantageously expanded in the corresponding direction.This differentiates the ascertained future course range KB from a pureforecast of the road progression. According to 47, future course rangeKB of the first vehicle is ascertained iteratively, i.e., a newdetermination cycle follows here. According to step 45, a preferredrefinement of the present invention provides for limiting the determinedfuture course range on the basis of stationary objects 25 and, in so faras present, with reference to detected oncoming vehicles F_(G) which arenot shown in FIGS. 2 and 3.

The following step 46 relates to the use of the method according to thepresent invention within the framework of an adaptive travel speed andproximity control. At this point, a vehicle in front is selected as acontrol object for the proximity control. In so doing, advantageouslyonly those vehicles in front are now taken into account which arelocated within the determined future course range KB. If a plurality ofpreceding-traveling vehicles are located in this range, a selection ispreferably made according to which of the preceding-traveling vehiclesrequires a lowest setpoint acceleration or a greatest setpointdeceleration for the controlled vehicle. However, the selection can alsobe made alternatively or additionally as a function of differentcriteria. For example, the selection can be made according to which ofthe preceding-traveling vehicles exhibits the smallest distance to thefirst controlled vehicle. Numeral 48 represents the iterative repetitionof the method according to the preferred embodiment of the presentinvention.

FIG. 5 shows a flow chart of a second exemplary embodiment of thepresent invention. Steps 51 through 54 correspond to steps 41 through 44according to FIG. 4. According to the second refinement of the presentinvention, a verified future course range KB_(ver) is then determined instep 55. For this purpose, according to 56, further measuring data,particularly a future course range KB₂ determined in another way, areused. For example, this otherwise determined future course range KB₂ canbe determined on the basis of the methods known from the related art,with the aid of a yaw rate or a transverse acceleration. By linking aplurality of future course ranges, ascertained independently of oneanother, an error rate existing in each case is further minimized. Inthe simplest case, the two determined future course ranges KB and KB₂are linked, such that the first determined course range KB is used aslong as a fixed minimal number of preceding-traveling vehicles isdetected. If fewer preceding-traveling vehicles than this fixed numberare detected, future course range KB₂ is used. Alternatively, the dataof both determined course ranges KB and KB₂ can also be correlated withone another to obtain verified course range KB_(ver). According to 58,the future verified course range is also determined iteratively. Step 57corresponds to step 46 of FIG. 4 and again includes an object selectionof a preceding-traveling vehicle within the framework of an adaptivetravel speed and proximity control.

FIG. 6 shows a detailed representation of the method steps fordetermining future course range KB according to steps 44 and 54 of FIGS.4 and 5. Accordingly, steps 61 through 63 can be inserted in place ofsteps 44 and 54 in FIGS. 4 and 5. In step 61, reference points S_(i) aredetermined by setting off positions P_(vi) of detectedpreceding-traveling vehicles F_(vi) against the associated determinedlateral offsets q_(i). In the ideal case, all the ascertained referencepoints S_(i) then lie on a curve which corresponds to future courseprogression KV of the first vehicle. This course progression KV isascertained in step 62, in that a function is ascertained, for examplein the form of a polynomial, which, to the greatest extent possible,includes all the reference points S_(i) at least approximatively. Thisdetermined function then describes future course progression KV. In step63, future course range KB is then determined, in that courseprogression KV is expanded by width b of the first vehicle. In addition,optionally, a further expansion E is preferably effected as a functionof detected lane-change signals of the first vehicle.

What is claimed is:
 1. A method for determining a future travel-course range of a first vehicle equipped with a proximity sensor, comprising the steps of: using the proximity sensor, determining at least two relative positions of one preceding-traveling vehicle with respect to the first vehicle; ascertaining lateral offsets between the preceding-traveling vehicle and the first vehicle on the basis of the at least two relative positions; ascertaining a future course range of the first vehicle as a function of a course progression of the preceding-traveling vehicle; forming the course progression of the preceding-traveling vehicle from the at least two determined relative positions of the preceding-traveling vehicle; forming reference points as a function of lateral offsets and of the course progression of the preceding-traveling vehicle; determining a function, corresponding to a future course progression of the first vehicle, which includes essentially all of the reference points; and expanding the future course progression of the first vehicle by a predetermined width, yielding the future course range of the first vehicle.
 2. The method according to claim 1, further comprising the steps of: determining a relative position of the preceding-traveling vehicle with respect to the first vehicle; based on the relative position, determining a lateral offset between the preceding-traveling vehicle and the first vehicle; and determining the future course range of the first vehicle as a function of the lateral offset and the course progression of the preceding-traveling vehicle.
 3. The method according to claim 2, further comprising the steps of: re-determining the lateral offset at predetermined instants; and assuming that the lateral offset is constant between the predetermined instants.
 4. The method according to claim 1, further comprising the steps of: determining the future course range on the basis of course progressions of a plurality of preceding-traveling vehicles; and isolating a travel-lane change of an individual preceding-traveling vehicle by one of a comparison, a correlation and an average of the course progressions of the plurality of preceding-traveling vehicles.
 5. The method according to claim 1, further comprising the steps of: determining at least one further future course range of the first vehicle on the basis of at least one of a steering angle, a steering-wheel angle, a yaw rate, a difference of wheel speeds, a transverse acceleration, stationary objects, and oncoming vehicles detected by the proximity sensor; and ascertaining a verified future course range as a function of the future course range and the at least one further future course range.
 6. The method according to claim 1, further comprising the steps of: limiting the future course range on the basis of positions of at least one of: detected stationary objects and detected oncoming vehicles.
 7. A device comprising: a proximity sensor for determining at least two relative positions of one preceding-traveling vehicle with respect to a first vehicle; an evaluation device for ascertaining at least an angle, a distance and a speed of the one preceding-traveling vehicle; means for ascertaining lateral offsets between the preceding-traveling vehicle and the first vehicle on the basis of the at least two relative positions; means for ascertaining a future course range of the first vehicle as a function of a course progression of the preceding-traveling vehicle; means for forming the course progression of the preceding-traveling vehicle from the at least two determined relative positions of the preceding-traveling vehicle; means for forming reference points as a function of lateral offsets and of the course progression of the preceding-traveling vehicle; means for determining a function, corresponding to a future course progression of the first vehicle, which includes essentially all of the reference points; and means for expanding the future course progression of the first vehicle by a predetermined width, yielding the future course range of the first vehicle. 